Regulating circuit including a plurality of low drop out regulators and method of operating the same

ABSTRACT

A regulating circuit including a first direct current (DC)-DC converter configured to apply a first supply voltage to a first node in a first mode and apply the first supply voltage to a second node in a second mode, a first low drop output (LDO) regulator connected to the first node, the first LDO regulator configured to provide an output voltage to an output node by regulating the first supply voltage of the first node, and a second LDO regulator connected to the first node, the second LDO regulator configured to provide an auxiliary current to the first node in the second mode may be provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2019-0037306, filed on Mar. 29, 2019, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

The inventive concepts relate to a regulating circuits for supplying avoltage by using a plurality of low drop output (LDO) regulators and aconverter, and/or methods of operating the same.

In general, the regulating circuit converts power input from the outsideinto direct current (DC) power desired by a system by using powerswitches. A power regulator included in a regulating circuit may be, forexample, a DC-DC converter for increasing or decreasing a voltage of theinput DC power. The LDO regulator as a linear regulator that operates ata low input and output potential difference is referred to as a lowdamage-type linear regulator or a low saturation-type linear regulator.Therefore, in order to output the same voltage, a low input voltage maybe desired by the LDO regulator.

In particular, the LDO regulator may include a load capacitor. Inaccordance with the size of the load capacitor, a magnitude of a ripplevoltage and a time for which an output voltage is stabilized may be in atrade-off relationship. Therefore, a structure of the regulating circuitcapable of decreasing the ripple voltage without increasing the size ofthe load capacitor included in the LDO regulator is desired.

SUMMARY

The inventive concepts provide regulating circuits for providing astable output voltage by decreasing a ripple voltage by using aplurality of low drop output (LDO) regulators and a converter, and/ormethods of operating the same.

The inventive concepts also provides regulating circuits for providing astable voltage to a plurality of nodes by using a plurality of DC-DCconverters, and/or methods of operating the same.

According to an example embodiment of the inventive concepts, aregulating circuit may include a first direct current (DC)-DC converterconfigured to apply a first supply voltage to a first node in a firstmode and apply the first supply voltage to a second node in a secondmode, a first low drop output (LDO) regulator connected to the firstnode, the first LDO regulator configured to provide an output voltage toan output node by regulating the first supply voltage of the first node,and a second LDO regulator connected to the first node, the second LDOregulator configured to provide an auxiliary current to the first nodein the second mode.

According to an example embodiment of the inventive concepts, aregulating circuit may include a first direct current (DC)-DC currentconfigured to provide a first supply voltage, a switching circuitconfigured to connect an output end of the first DC-DC converter to oneof a first node or a second node based on a mode setting signal, a firstlow drop output (LDO) regulator configured to provide an output voltageto an output node by regulating a voltage of the first node, and asecond LDO regulator configured to increase a voltage level of the firstnode to that of the first supply voltage by supplying an output currentto the first node when the first DC-DC converter is connected to thesecond node.

According to an example embodiment of the inventive concepts, a methodof operating a regulating circuit for supplying an output voltage byregulating a voltage of a first node may include switching an output endof a first direct current (DC)-DC converter from the first node to asecond node, applying an auxiliary current to the first node by a firstlow drop output (LDO) regulator, and supplying the output voltage byregulating a voltage of the first node by a second LDO regulator.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the inventive concepts will be more clearly understoodfrom the following detailed description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a block diagram illustrating an electronic device according toan example embodiment of the inventive concepts;

FIG. 2 is a circuit diagram illustrating a regulating circuit accordingto an example embodiment of the inventive concepts;

FIG. 3 is a timing diagram illustrating an operation of a regulatingcircuit according to an example embodiment of the inventive concepts;

FIG. 4 is a circuit diagram illustrating a regulating circuit accordingto an example embodiment of the inventive concepts;

FIG. 5 is a table illustrating a switching operation of a regulatingcircuit according to an example embodiment of the inventive concepts;

FIGS. 6A to 6D are circuit diagrams illustrating operations of theregulating circuit of FIG. 4;

FIG. 7 is a view illustrating a regulating circuit according to anexample embodiment of the inventive concepts;

FIG. 8 is a timing diagram illustrating an operation of a regulatingcircuit according to an example embodiment of the inventive concepts;

FIG. 9 is a block diagram illustrating a regulating circuit according toan example embodiment of the inventive concepts;

FIG. 10 is a flowchart illustrating a method of operating a regulatingcircuit, according to an example embodiment of the inventive concepts;

FIG. 11 is a flowchart illustrating a method of operating a regulatingcircuit, according to an example embodiment of the inventive concepts;

FIG. 12 is a flowchart illustrating a method of operating a currentassist circuit, according to an example embodiment of the inventiveconcepts; and

FIG. 13 is a block diagram illustrating an electronic device, accordingto an example embodiment of the inventive concepts.

DETAILED DESCRIPTION

FIG. 1 is a block diagram illustrating an electronic device 10 accordingto an example embodiment of the inventive concepts.

Referring to FIG. 1, the electronic device 10 may include a regulatingcircuit 100, a power supply 300, and a control logic 400. The powersupply 300 may generate a plurality of power voltages based on anexternal power voltage, and provide an input voltage Vin among theplurality of power voltages to the regulating circuit 100.

The regulating circuit 100 may include a first low drop out (LDO)regulator LDO1, a second LDO regulator LDO2, and a direct current(DC)-DC converter DDC, and generate an output voltage Vout by regulatingthe input voltage Vin received from the power supply 300. In an exampleembodiment, the regulating circuit 100 may receive a mode setting signalSig_MS from the control logic 400, and provide various voltages to aplurality of nodes based on the mode setting signal Sig_MS. The controllogic 400 may generate the mode setting signal Sig_MS in response to asupply voltage request signal for at least one of the plurality ofnodes.

The DC-DC converter DDC may receive the DC input voltage Vin, increasesor decreases the DC input voltage Vin, and output a DC voltage. In anexample, the DC-DC converter DDC may be implemented by a step-downconverter or a buck converter. In an example embodiment, the DC-DCconverter DDC may provide a voltage to the plurality of nodes based onthe mode setting signal Sig_MS. In an example embodiment, the DC-DCconverter DDC may decrease the input voltage Vin based on the modesetting signal Sig_MS received from the control logic 400, and providethe decreased input voltage Vin to the first LDO regulator LDO1 oranother device through a first node or a second node.

The first LDO regulator LDO1 may provide the output voltage Vout havinga particular value by regulating the decreased voltage received from theDC-DC converter DDC to another device or a functional block of theelectronic device 10.

The second regulator LDO2 may be connected to the first LDO regulatorLDO1 through the first node. According to an example embodiment, theDC-DC converter DDC may stop providing a voltage to the first LDOregulator LDO1. In an example embodiment, as described above, the DC-DCconverter DDC may provide the voltage to the second node, instead of thefirst node connected to the first LDO regulator LDO1, based on the modesetting signal Sig_MS.

Each of the first LDO regulator LDO1 and the second LDO regulator LDO2may include a load capacitor, an amplifier for amplifying a differencebetween a reference voltage and a feedback voltage, and a powertransistor for providing a final output voltage based on an outputvoltage of the amplifier. In an example embodiment, the first LDOregulator LDO1 and the second LDO regulator LDO2 may include differentkinds of power transistors. In an example embodiment, the first LDOregulator LDO1 may include an n-channel metal-oxide semiconductor (NMOS)transistor as the power transistor, and the second LDO regulator LDO2may include a p-channel metal-oxide semiconductor (PMOS) transistor asthe power transistor.

According to some example embodiments of the inventive concepts, thesecond LDO regulator LDO2 may output an auxiliary current to the firstnode in a period in which the DC-DC converter DDC does not provide thevoltage, and accordingly, a voltage level of the first node may not bedecreased. Thus, even in the period in which the DC-DC converter DDCdoes not provide the voltage, a stable voltage may be input to the firstLDO regulator LDO1.

FIG. 2 is a circuit diagram illustrating a regulating circuit 100according to an example embodiment of the inventive concepts.Description previously given with reference to FIG. 1 is omitted.

Referring to FIG. 2, the regulating circuit 100 may include a DC-DCconverter 110, a switching circuit 120, a first LDO regulator 130, and asecond LDO regulator 140. The DC-DC converter 110 may be connected to afirst node N1 and a second node N2 through the switching circuit 120.The switching circuit 120 may include a first switch SW1 and a secondswitch SW2. The first switch SW1 may electrically connect or disconnectthe DC-DC converter 110 and the first node N1 based on a first modesignal MS1. The second switch SW2 may electrically connect or disconnectthe DC-DC converter 110 and the second node N2 based on a second modesignal MS2. In an example embodiment, the first mode signal MS1 and thesecond mode signal MS2 may be received from the control logic 400(FIG. 1) as the mode setting signals Sig_MS.

The first switch SW1 and the second switch SW2 may be configured byvarious switch devices that are capable of controlling electricalconnections based on external signals. In an example, the first switchSW1 and the second switch SW2 may be configured by transistors. In anexample embodiment, the first switch SW1 and the second switch SW2 maycomplementarily operate.

In an example, in a first mode, the first switch SW1 may be shorted (inother words, turned-on) and the second switch SW2 may be opened (inother words, turned-off), and thus, the DC-DC converter 110 may beconnected to the first node N1. Therefore, a supply voltage providedfrom the DC-DC converter 110 may be provided to the first LDO regulator130 through the first node N1. Further, in a second mode, the firstswitch SW1 may be opened and the second switch SW2 may be shorted andaccordingly, the DC-DC converter 110 may be connected to the second nodeN2. Therefore, the supply voltage provided from the DC-DC converter 110may be provided to an external device through the second node N2.

The first LDO regulator 130 may generate an output voltage by regulatinga voltage of the first node N1, and provide the generated output voltageto the external device through an output node Nout. In the first mode,the first LDO regulator 130 may generate the output voltage by receivingthe supply voltage provided from the DC-DC converter 110 through thefirst node N1 and regulating the received supply voltage.

In the second mode, the second LDO regulator 140 may output an auxiliarycurrent I_aux to the first node N1. Thus, even when the first switch SW1is opened, a phenomenon that no voltage is supplied to the first nodeN1, may be avoided. The first LDO regulator 130 may generate the outputvoltage by receiving a voltage from the second LDO regulator 140 throughthe first node N1 and regulating the received voltage.

According to some example embodiments of the inventive concepts, like inthe above-described second mode, even when the DC-DC converter 110 doesnot provide a supply voltage to the first LDO regulator 130 but providesto another node in accordance with an additional request, the first LDOregulator 130 may receive a voltage from the second LDO regulator 140.Therefore, a stable output voltage may be generated.

In FIG. 2, an example in which connections between the DC-DC converter110 and the first node N1 and the second node N2 are controlled by thetwo switches SW1 and SW2 is illustrated. However, example embodiments ofthe inventive concepts are not limited thereto. According to someexample embodiments, connections between the DC-DC converter 110 and thefirst node N1 and the second node N2 may be controlled through more thantwo switch devices.

FIG. 3 is a timing diagram illustrating an operation of a regulatingcircuit according to an example embodiment of the inventive concepts.The X axis of FIG. 3 illustrates time, and the Y axis of FIG. 3illustrates an electric potential of a node or a logic level of asignal.

Referring to FIGS. 2 and 3, in a first mode Md1, the first mode signalMS1 may maintain logic high, and the second mode signal MS2 may maintainlogic low. The first switch SW1 may be shorted (ON), and the secondswitch SW2 may be opened (OFF) based on the first mode signal MS1 andthe second mode signal MS2. Therefore, the DC-DC converter 110 may beconnected to the first node N1 and a supply voltage having a stableripple may be provided to the first node N1, and thus a voltage of theoutput node Nout may also have a stable ripple.

As a mode changes from the first mode Md1 to a second mode Md2, thefirst mode signal MS1 may be transitioned from logic high to logic lowand the second mode signal MS2 may be transitioned transited from logiclow to logic high. The first switch SW1 may be opened (OFF) and thesecond switch SW2 may be shorted (ON) based on the first mode signal MS1and the second mode signal MS2. Therefore, the DC-DC converter 110 isconnected to the second node N2 and the supply voltage may be providedto the second node N2.

Because the supply voltage is not provided to the first node N1, levelsof the voltage of the first node N1 and a voltage of the output nodeNout, which is generated by regulating the voltage of the first node N1,may temporarily decrease. However, the voltage level of the first nodeN1 may be recovered to be the same as or substantially similar to thatin the first mode Md1 by the second LDO regulator 140 outputting theauxiliary current I_aux. Further, the level of the voltage of the outputnode Nout, which is generated by regulating the voltage of the firstnode N1, may be recovered to be the same as or substantially similar tothat in the first mode Md1.

According to some example embodiments of the inventive concepts, even inthe second mode Md2 in which the supply voltage of the DC-DC converter110 is not provided to the first note N1, the voltage of the output nodeNout may have a stable ripple by the second LDO regulator 140 byproviding the auxiliary current I_aux.

FIG. 4 is a circuit diagram illustrating a regulating circuit 200according to an example embodiment of the inventive concepts.Description previously given with reference to FIG. 2 is omitted.

Referring to FIG. 4, the regulating circuit 200 may include a firstDC-DC converter 211, a second DC-DC converter 212, a switching circuit220, a first LDO regulator 230, and a second LDO regulator 240. Becauseoperations of the first DC-DC converter 211, the first LDO regulator230, and the second LDO regulator 240 are the same as or substantiallysimilar to those of the DC-DC converter 110, the first LDO regulator130, and the second LDO regulator 140 of FIG. 2, description previouslygiven with reference to FIG. 2 is omitted.

The switching circuit 220 may include first to fifth switches SW1 toSW5. Because the first switch SW1 and the second switch SW2 aredescribed in detail with reference to FIG. 2, description thereof isomitted. The third switch SW3 may electrically connect or disconnect thefirst DC-DC converter 211 and a third node N3 based on a third modesignal MS3 Likely, the fourth switch SW4 may electrically connect ordisconnect the second DC-DC converter 212 and the second node N2 basedon a fourth mode signal MS4, and the fifth switch SW5 may electricallyconnect or disconnect the second DC-DC converter 212 and the third nodeN3 based on a fifth mode signal MS5.

The first to fifth switches SW1 to SW5 may be configured by variousswitch devices that are capable of controlling electrical connectionsbased on external signals (for example, the first to fifth mode signalsMS1 to MS5). In an example, the first to fifth switches SW1 to SW5 maybe configured by transistors. In an example embodiment, the first tofifth mode signals MS1 to MS5 may be received from the control logic 400(FIG. 1) as the mode setting signals Sig_MS.

In accordance with an operation of the switching circuit 220, the firstDC-DC converter 211 may be connected to one of the first node N1, thesecond node N2, or the third node N3, and may supply a first supplyvoltage to one of the first node N1, the second node N2, or the thirdnode N3. The second DC-DC converter 212 may be connected to at least oneof the second node N2 or the third node N3, and may provide a secondsupply voltage to at least one of the second node N2 or the third nodeN3. In an example embodiment, the second supply voltage provided by thesecond DC-DC converter 212 may have a level higher or lower than that ofthe first supply voltage provided by the first DC-DC converter 211.

According to an example embodiment of the inventive concepts, when thesecond DC-DC converter 212 provides a voltage for the plurality of nodes(for example, the second node N2 and the third node N3), the first DC-DCconverter 211 may not be connected to the first node N1 and may beconnected to another node (e.g., the second node N2 or the third nodeN3). That is, before the second DC-DC converter 212 applies the secondsupply voltage to the second node N2 and the third node N3, the firstDC-DC converter 211 may first increase and decrease a voltage level ofthe second node N2 or the third node N3. The voltage level of the secondnode N2 or the third node N3 may be increased and decreased within ashort time.

Further, according to an embodiment of the inventive concepts, even whenthe first DC-DC converter 211 is used for increasing and decreasing thevoltage level of another node (e.g., the second node N2 or the thirdnode N3), instead of increasing and decreasing the voltage level of thefirst node N1, the second LDO regulator 240 may maintain the voltagelevel of the first node N1, and thus the first LDO regulator 230 maystably provide an output voltage to the output node Nout.

FIG. 4 illustrates an example in which the regulating circuit 200provides a voltage to the outside (e.g., other devices in the electronicdevice 10 (FIG. 1) through the three nodes Nout, N2, and N3. However,example embodiments of the inventive concepts are not limited thereto.In some example embodiments, the regulating circuit 200 may provide thevoltage to the outside through more or less than three nodes.

The control logic 400 may provide the second mode signal MS2 and thethird mode signal MS3 based on (or alternatively, in response to) asupply voltage request signal for at least one of the second node or thethird node. In other words, the regulating circuit may receive thesecond mode signal MS2 and the third mode signal MS3 that have beengenerated based on (or alternatively, in response to) a supply voltagerequest signal for at least one of the second node or the third node.

FIG. 5 is a table illustrating a switching operation of a regulatingcircuit according to an example embodiment of the inventive concepts.FIGS. 6A to 6D are circuit diagrams illustrating operations of theregulating circuit 200 of FIG. 4 s.

Referring to FIGS. 4 and 5, the regulating circuit 200 may operate inone of the first mode Md1, the second mode Md2, a third mode Md3, and afourth mode Md4. In the first mode Md1, the first DC-DC converter 211may apply the first supply voltage to the first node N1, and the secondDC-DC converter 212 may apply the second supply voltage to the secondnode N2.

In the second mode Md2, in accordance with a request of the controllogic 400 (FIG. 1), the second DC-DC converter 212 may apply the secondsupply voltage to the second node N2, and the first DC-DC converter 211may apply the first supply voltage to the third node N3.

In the third mode Md3, after the third node N3 has the first supplyvoltage in the second mode Md2, the second DC-DC converter 212 may applythe second supply voltage to the third node N3 and the first DC-DCconverter 211 may apply the first supply voltage to the first node N1again.

In the fourth mode Md4, in accordance with a request of the controllogic 400 (FIG. 1), the second DC-DC converter 212 may apply the secondsupply voltage to the third node N3 and the first DC-DC converter 211may apply the first supply voltage to the second node N2.

After the fourth mode Md4, the operation in the first mode Md1 may beperformed again, and the operations in the first mode Md1 to the fourthmode Md4 may be repeated.

FIG. 6A illustrates an example in which the regulating circuit 200operates in the first mode Md1. Referring to FIGS. 5 and 6A, in thefirst mode Md1, the first switch SW1 and the fourth switch SW4 areshorted (ON) and the second switch SW2, the third switch SW3, and thefifth switch SW5 may be opened (OFF).

As the first switch SW1 is shorted, the first DC-DC converter 211 mayprovide the first supply voltage Vs1 to the first node N1. The first LDOregulator 240 may provide an output voltage Vout to the output node Noutby regulating the first supply voltage Vs1 of the first node N1. As thefourth switch SW4 is shorted, the second DC-DC converter 212 may supplythe second supply voltage Vs2 to the second node N2. The third node N3may maintain a floating state.

FIG. 6B illustrates an example in which the regulating circuit 200operates in the second mode Md2. Referring to FIGS. 5 and 6B, in thesecond mode Md2, the third switch SW3 and the fourth switch SW4 areshorted (ON) and the first switch SW1, the second switch SW2, and thefifth switch SW5 may be opened (OFF).

As the fourth switch SW4 is shorted, the second DC-DC converter 212 maysupply the second supply voltage Vs2 to the second node N2. As the thirdswitch SW3 is shorted, the first DC-DC converter 211 may supply thefirst supply voltage Vs1 to the third node N3. A connection between thefirst node N1 and the first DC-DC converter 211 may be cut off. Avoltage level of the first supply voltage Vs1 may be recovered by theauxiliary current I_aux generated by the second LDO regulator 230.Therefore, although the connection between the first node N1 and thefirst DC-DC converter 211 is cut off, the first LDO regulator 240 mayprovide the output voltage Vout to the output node Nout by regulatingthe first supply voltage Vs1 of the first node N1.

FIG. 6C illustrates an example in which the regulating circuit 200operates in the third mode Md3. Referring to FIGS. 5 and 6C, in thethird mode Md3, the first switch SW1 and the fifth switch SW5 areshorted (ON) and the second switch SW2, the third switch SW3, and thefourth switch SW4 may be opened (OFF).

As the first switch SW1 is shorted, the first DC-DC converter 211 mayprovide the first supply voltage Vs1 to the first node N1. The first LDOregulator 240 may stably provide the output voltage Vout to the outputnode Nout by regulating the first supply voltage Vs1 of the first nodeN1. As the fifth switch SW5 is shorted, the second DC-DC converter 212may supply the second supply voltage Vs2 to the third node N3.

FIG. 6D illustrates an example in which the regulating circuit 200operates in the fourth mode Md4. Referring to FIGS. 5 and 6D, in thefourth mode Md4, the second switch SW2 and the fifth switch SW5 areshorted (ON) and the first switch SW1, the third switch SW3, and thefourth switch SW4 may be opened (OFF).

As the fifth switch SW5 is shorted, the second DC-DC converter 212 maysupply the second supply voltage Vs2 to the third node N3. As the secondswitch SW2 is shorted, the first DC-DC converter 211 may supply thefirst supply voltage Vs1 to the second node N2. The connection betweenthe first node N1 and the first DC-DC converter 211 may be cut off. Thevoltage level of the first supply voltage Vs1 may be recovered by theauxiliary current I_aux generated by the second LDO regulator 230.Therefore, although the connection between the first node N1 and thefirst DC-DC converter 211 is cut off, the first LDO regulator 240 mayprovide the output voltage Vout to the output node Nout by regulatingthe first supply voltage Vs1 of the first node N1.

FIG. 7 is a view illustrating a regulating circuit 100 according to anexample embodiment of the inventive concepts. Description previouslygiven with reference to FIG. 2 is omitted.

Referring to FIG. 7, the regulating circuit 100 may include the DC-DCconverter 110, the switching circuit 120, the first LDO regulator 130,the second LDO regulator 140, and a current assist circuit 150. Becausethe DC-DC converter 110, the switching circuit 120, the first LDOregulator 130, and the second LDO regulator 140 are described in detailwith reference to FIG. 2, description thereof is omitted.

The current assist circuit 150 may sense an output current I_out of theoutput node Nout, and may output an assist current I_ast to the firstnode N1 based on the sensed output current I_out. In an exampleembodiment, the current assist circuit 150 may include a current mirrorcircuit. During transition from the first mode to the second mode,charges may be stored in a capacitor of the first node N1 in order toprovide an output current leaks toward an output node, therebycompensating a temporary decrease of a voltage level of the first nodeN1.

According to an example embodiment of the inventive concepts, thecurrent assist circuit 150 may output the assist current I_ast in aperiod in which the voltage level of the first node N1 is temporarilydecreased. Therefore, the voltage level of the first node N1 may not bedecreased, thereby maintaining the first supply voltage. As a result, inspite of the transition from the first mode to the second mode, a stablevoltage with a smallest ripple may be applied to the first LDO regulator130 and the output voltage may be also stably maintained.

FIG. 7 illustrates an example embodiment in which the current assistcircuit 150 senses a current applied to the output node Nout. However,example embodiments of the inventive concepts are not limited thereto.In some example embodiment, the current assist circuit 150 may sense acurrent applied to the first LDO regulator 130 or a current applied tothe second node N2, and may apply the assist current I_ast to the firstnode N1 based on the sensed current.

FIG. 8 is a timing diagram illustrating an operation of a regulatingcircuit according to an example embodiment of the inventive concepts.The X axis of FIG. 8 illustrates time and the Y axis of FIG. 8illustrates an electric potential of a node or a logic level of asignal. Description previously given with reference to FIG. 3 isomitted.

Referring to FIGS. 7 and 8, dashed lines illustrate an operation of theregulating circuit 100 without the current assist circuit 150 and solidlines illustrate an operation of the regulating circuit 100 with thecurrent assist circuit 150. Because the dashed lines may be the same asor substantially similar to the graphs of FIG. 3, description thereofwill be omitted.

During transition from the first mode Md1 to the second mode Md2, thesecond LDO regulator 140 may have a long stabilizing time. Therefore,when the current assist circuit 150 is omitted, the voltage levels ofthe first node N1 and the output node Nout may temporarily decrease.

In an example embodiment, the current assist circuit 150 may have ashorter current supply time than the second LDO regulator 140.Therefore, before the second LDO regulator 140 outputs the auxiliarycurrent I_aux to the first node N1, the current assist circuit 150 mayoutput the assist current I_ast to the first node N1.

According to an example embodiment of the inventive concepts, after theconnection between the first node N1 and the DC-DC converter 110 is cutoff, the first node N1 may uniformly maintain the voltage level by theassist current I_ast. Then, the first node N1 may uniformly maintain thevoltage level by the stably output auxiliary current I_aux. As thevoltage with the smallest ripple (or alternatively, ripple having areduced height) is applied to the first node N1, the voltage level ofthe output node Nout may be stably maintained.

FIG. 9 is a block diagram illustrating a regulating circuit 200 aaccording to an example embodiment of the inventive concepts.Description previously given with reference to FIG. 4 is omitted.

Referring to FIG. 9, the regulating circuit 200 a may include a firstDC-DC converter 211 a, a second DC-DC converter 212 a, a third DC-DCconverter 213 a, a switching circuit 220 a, a sixth switch SW6, and anLDO regulator 230 a. Because operations of the first DC-DC converter 211a, the second DC-DC converter 212 a, the switching circuit 220 a, andthe LDO regulator 230 a are the same as or substantially similar tothose of the first DC-DC converter 211, the second DC-DC converter 212,the switching circuit 220, and the first LDO regulator 230 of FIG. 4,description previously given with reference to FIG. 4 is omitted.

An operation of the third DC-DC converter 213 a is similar to that ofthe second LDO regulator 240 of FIG. 4. In the second mode in which aconnection between the first DC-DC regulator 211 a and the first node N1is cut off, the third DC-DC regulator 213 a is connected to the firstnode N1, and may provide the first supply voltage to the first node N1.The third DC-DC regulator 213 a may provide an output voltage (e.g., thefirst supply voltage), which is the same as or substantially similar tothat of the first DC-DC regulator 211 a. Therefore, even when the firstDC-DC regulator 211 a does not provide a voltage to the LDO regulator230 a, the LDO regulator 230 a may receive the first supply voltage fromthe third DC-DC regulator 213 a. In an example, the third DC-DCregulator 213 a may be configured by a step-down converter or a buckconverter.

The sixth switch SW6 may electrically connect or disconnect the thirdDC-DC regulator 213 a and the first node N1 based on a sixth mode signalMS6. In an example embodiment, the sixth switch SW6 may complementarilyoperate with the first switch SW1. That is, when the first switch SW1 isopened, the sixth switch SW6 may be shorted, and when the first switchSW1 is shorted, the sixth switch SW6 may be opened.

FIG. 10 is a flowchart illustrating a method of operating a regulatingcircuit 100, according to an example embodiment of the inventiveconcepts.

Referring to FIGS. 2 and 10, the regulating circuit 100 may switch anoutput end of the DC-DC converter 110 from the first node N1 to thesecond node N2 in operation S110. When the connection between the firstnode N1 and the DC-DC converter 110 is cut off, the second LDO regulator140 may apply the auxiliary current I_aux to the first node N1 inoperation S120. The first LDO regulator 130 may provide an outputvoltage to the output node Nout by regulating the voltage of the firstnode N1.

FIG. 11 is a flowchart illustrating a method of operating a regulatingcircuit, according to an example embodiment of the inventive concepts.

Referring to FIGS. 4 and 11, in the first mode, the regulating circuit100 may connect an output end of the first DC-DC converter 211 to thefirst node N1, and may connect an output end of the second DC-DCconverter 212 to the second node N2 in operation S210. In the secondmode, the regulating circuit 100 may switch an output end of the firstDC-DC converter 211 from the first node N1 to the third node N3 inoperation S220. In the third mode, the regulating circuit 100 may switchthe output end of the first DC-DC converter 211 from the third node N3to the first node N1 and may switch the output end of the second DC-DCconverter 212 from the second node N2 to the third node N3 in operationS230. In the fourth mode, the regulating circuit 100 may switch theoutput end of the first DC-DC converter 211 from the first node N1 tothe second node N2 in operation S240.

Therefore, the first node N1 may have the first supply voltage by theauxiliary current I_aux generated by the second LDO regulator 230, thesecond node N2 may have the first supply voltage by the first DC-DCconverter 211, and the third node N3 may have the second supply voltageby the second DC-DC converter 212. Then, the first DC-DC converter 211may be switched from the second node N2 to the first node N1, and mayoperate in the first mode. FIG. 12 is a flowchart illustrating a methodof operating a current assist circuit, according to an exampleembodiment of the inventive concepts.

Referring to FIGS. 7 and 12, the current assist circuit 150 may sense anoutput current applied from or to the output node Nout of the regulatingcircuit 100. The current assist circuit 150 may apply the assist currentI_ast to the first node N1 based on the sensed output current.

FIG. 13 is a block diagram illustrating an electronic device 3000according to an example embodiment of the inventive concepts.

Referring to FIG. 13, the electronic device 3000 may include a powersupply 3100, a central processing unit (CPU) 3200, a signal processingunit 3300, a user interface 3400, a storage unit or a memory 3500, adevice interface 3600, and a bus 3700.

The electronic device 3000 may be, for example, a computer, a mobilephone, a personal digital assistant (PDA), a portable media player(PMP), an MP3 player, a camera, a camcorder, a TV set, or a displaydevice.

The power supply 3100 may generate a power voltage for the electronicdevice 3000, and may supply the generated power voltage to therespective elements. The regulating circuit 100 according to an exampleembodiment of the inventive concepts may be applied to the power supply3100. For example, the power supply 3100 may include a plurality of LDOregulators, and may stably manage a voltage level of an output voltageeven when a DC-DC converter supplies a voltage to another node (in otherwords, even when a DC-DC converter does not supply a voltage to thefirst node).

The CPU 3200 may control the electronic device 3000. For example, theCPU 3200 may control the elements of the electronic device 3000 based oninformation input through the user interface 3400.

The signal processing unit 3300 may process a signal received throughthe device interface 3600 or a signal read from the storage unit 3500 inaccordance with a determined standard. For example, the signalprocessing unit 3300 may process a video signal or an audio signal.

The user interface 3400 may be an input device for a user settinginformation for setting a function of the electronic device 3000 andoperating the electronic device 3000. The storage unit 3500 may storevarious information items needed for operating the electronic device3000. Further, data received through the device interface 3600 or dataitems processed by the electronic device 3000 may be stored in thestorage unit 3500.

The device interface 3600 may perform data communication with anexternal device connected to the electronic device 3000 by wire orwirelessly. The bus 3700 may transmit information among the elements ofthe electronic device 3000.

While the inventive concepts have been particularly shown and describedwith reference to some example embodiments thereof, it will beunderstood that various changes in form and details may be made thereinwithout departing from the spirit and scope of the following claims.

What is claimed is:
 1. A regulating circuit comprising: a first directcurrent (DC)-DC converter configured to generate a first supply voltage,apply the first supply voltage to a first node in a first mode via afirst switch, and apply the first supply voltage to a second node in asecond mode via a second switch; a first low drop output (LDO) regulatorconnected to the first node, the first LDO regulator configured to beselectively connected to the first DC-DC converter via the first switchto receive the first supply voltage, the first LDO regulator configuredto provide an output voltage to an output node by regulating the firstsupply voltage; and a second LDO regulator directly connected to thefirst node, the second LDO regulator configured to provide an auxiliarycurrent to the first node when the first DC-DC converter does not applythe first supply voltage to the first node via the first switch andsupplies the first supply voltage to the second node via the secondswitch.
 2. The regulating circuit of claim 1, further comprising: thecontrol logic configured to generate a first mode signal correspondingto the first mode, a second mode signal corresponding to the secondmode, and a third mode signal corresponding to a third mode, wherein thefirst switch is configured to electrically connect or disconnect thefirst node and the first DC-DC converter based on the first mode signal,the second switch is configured to electrically connect or disconnectthe second node and the first DC-DC converter based on the second modesignal, and the first DC-DC converter is further configured to apply thefirst supply voltage to a third node via a third switch based on thethird mode signal.
 3. The regulating circuit of claim 2, furthercomprising: a second DC-DC converter configured to provide a secondsupply voltage to the second node in the first mode via a fourth switchand provide the second supply voltage to the third node in the secondmode via a fifth switch.
 4. The regulating circuit of claim 3, whereinthe fourth switch configured to electrically connect or disconnect thesecond node and the second DC-DC converter based on the first modesignal and the third mode signal; and the fifth switch configured toelectrically connect or disconnect the third node and the second DC-DCconverter based on a fourth mode signal corresponding to a fourth modeand the second mode signal.
 5. The regulating circuit of claim 3,wherein the regulating circuit is configured to receive the second modesignal and the third mode signal generated based on a supply voltagerequest signal for at least one of the second node or the third node. 6.The regulating circuit of claim 5, further comprising: a switchingcircuit including the first switch and the second switch, the switchingcircuit configured to connect or disconnect the first DC-DC converterand the second node based on the second mode signal, and connect ordisconnect the second DC-DC converter to the second node based on thefirst mode signal or the third mode signal.
 7. The regulating circuit ofclaim 1, further comprising: a current assist circuit connected to thefirst node and the output node, the current assist circuit configured tosense a current of the output node and provide an assist current to thefirst node when the first DC-DC converter does not supply the firstsupply voltage to the first node via the first switch and supplies thefirst supply voltage to the second node via the second switch.
 8. Theregulating circuit of claim 7, wherein the current assist circuit is acurrent mirror configured to sense the current of the output node anddetermine a current level of the assist current based on the sensedcurrent.
 9. The regulating circuit of claim 1, wherein the first LDOregulator and the second LDO regulator comprise different kinds of metaloxide semiconductor (MOS) transistors.
 10. The regulating circuit ofclaim 9, wherein the first LDO regulator comprises at least onen-channel MOS (NMOS) transistor, and the second LDO regulator comprisesat least one p-channel MOS (PMOS) transistor.
 11. A regulating circuitcomprising: a first direct current (DC)-DC converter configured togenerate a first supply voltage; a switching circuit including a firstswitch and a second switch, the first switch configured to connect ordisconnect an output end of the first DC-DC converter to a first nodeand the second switch configured to connect or disconnect the output endof the first DC-DC converter to a second node based on a mode settingsignal; a first low drop output (LDO) regulator configured to provide anoutput voltage to an output node by regulating the first supply voltageon the first node; and a second LDO regulator directly connected to thefirst node, the second LDO regulator configured to maintain a level ofthe first supply voltage by supplying a current to the first node whenthe first DC-DC converter is not connected to the first node andconnected to the second node and supplies the first supply voltage tothe second node.
 12. The regulating circuit of claim 11, furthercomprising: a second DC-DC converter configured to generate a secondsupply voltage, wherein the switching circuit includes a fourth switchand a fifth switch, the fourth switch configured to connect ordisconnect an output end of the second DC-DC converter to the secondnode and the fifth switch configured to connect or disconnect the outputend of the second DC-DC converter to a third node based on the modesetting signal.
 13. The regulating circuit of claim 12, wherein theswitching circuit includes a third switch configured to connect ordisconnect the output end of the first DC-DC converter to the thirdnode, based on the mode setting signal.
 14. The regulating circuit ofclaim 11, further comprising: a current assist circuit connected to thefirst node and the output node, the current assist circuit configured tosense a current of the output node and apply an assist current to thefirst node based on the sensed current when the first switch disconnectsthe output of the first DC-DC converter to the first node and the secondswitch connects the output of the first-DC-DC converter to the secondnode.
 15. A method of operating a regulating circuit for supplying anoutput voltage to an output node by regulating a voltage of a firstnode, the method comprising: switching an output end of a first directcurrent (DC)-DC converter from the first node to a second node; applyingan auxiliary current to the first node by a first low drop output (LDO)regulator directly connected to the first node in response to adisconnection between the output end of the first DC-DC converter andthe first node and a connection between the output end of the firstDC-DC converter and the second node; and supplying the output voltage byregulating the voltage of the first node by a second LDO regulator. 16.The method of claim 15, further comprising: switching an output end of asecond DC-DC converter from a third node to the second node; andswitching the output end of the first DC-DC converter from the secondnode to the first node.
 17. The method of claim 16, further comprising:applying an assist current generated by a current assist circuit to thefirst node.
 18. The method of claim 17, wherein the applying an assistcurrent comprises: sensing a current of the output node; and applyingthe assist current, a current level of which has been determined basedon the sensed current of the output node, to the first node in responseto a disconnection between the output end of the first DC-DC converterand the first node and a connection between the output end of the firstDC-DC converter and the second node.
 19. The method of claim 17, whereinthe applying the assist current is performed after the switching theoutput end of the first DC-DC converter from the first node to thesecond node.